In a lighting device, primary energy—usually electrical energy—supplied thereto is converted into light, i.e. radiation having a wavelength in the visible range. Although the efficiency of the energy conversion from the primary energy into light energy may be quite high, still a portion of the primary energy will be converted into heat energy when generating light energy. The heat that is generated in the lighting device needs to be discharged to avoid temperatures in the lighting device to rise beyond acceptable limits.
Reference US 2009/0073688 discloses a light fixture including a member having a substantially frusto-conical shape. Light emitting diodes, LEDs, are disposed on the member. A channel in the member is configured to transfer heat generated by the LEDs through convection.
Reference US 2010/0314985 discloses a LED light bulb having a hollow LED support/heat sink with fins extending internally. Heat generated by the LEDs is conducted through the heat sink fins and is removed by a convectively driven air flow that flows through the LED support/heat sink.
For higher lighting outputs and/or lower construction volumes of the lighting device, the reference explains that passive cooling may be insufficient, and active cooling should be applied, e.g. by application of a cooling fan drawing air through the LED support, or by application of a corona discharge air pump to stimulate air flow through the LED support.
However, an additional component like a cooling fan requires additional space in the lighting device, requires energy, and may involve a device having moving parts which are susceptible to wear and produce noise.